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1 <br /> Mr. Marty Hartzell Project 803026 <br /> September 8, 20M <br /> Page 3 <br /> floating hydrocarbon data may not be representative of subsufce conditions. As a <br /> result, it is recommended that the proposed growdwater extraction well GWX-1 be used <br /> to evaluate current Fleming hydrocarbon d the 60l East Miner Street site during future <br /> groundwater monitoring and sampling events. In addition, 3PHg and BTEX <br /> concentrations in MW-1 and MW-3 have decreased by a factor of ten during the last six <br /> years. When combined with the trends observed in the perimetamonilming wells, these <br /> results indicate that the dissolved hydrocarbon impacts a the 601 East Miner Street site <br /> have attenuated as a result of natural processes. In addition, there is evidence that fire <br /> rated and magnitude of dissolved hydrocarbon impact W (his site is stable and likely <br /> declining. As a result, groundwater extraction and treatment is not warranted fro plume <br /> containment at the 601 East Miner Sheet site. <br /> The feasibility for using groundwater extraction and treewent was further evaluated by <br /> reviewing the bio-attonsration feasibility study performed by Verse Inc. in PPy7. The <br /> bin-attenuation study compared sail samples collection from one boring (VX-1) located <br /> ear fire scene zone and from two borings (BB-14 and BH-17) located outside and <br /> downgsdied of the dissolved phase impact and two groundwater samples collected <br /> Gem (B14-14 and BH-17) located dewmgradied and outside the groundwater impacts. In <br /> ground, the results of this study indicate the conditions in the subsurface would support <br /> crobial degradation of fuel-related hydrocarbons. The study also showed that <br /> significant populations of hydrocarbon degrading microbes were detected in sail and <br /> groundwater beneath the 601 East Miner Street site, and it appears the hydrocarbon <br /> degrades am the deminecpopulation of microbes in the fuel-iuµwc[ed area Asa result, <br /> the preliminary bio-altremation feasibility study indicates that biological processes are a <br /> significant component of the natural processes that have stabilized and redmed the <br /> hydrocarbon mass inthe subsurface at this site. These results indicate that a remedial <br /> slalegy that mace on moniand cannot attenuation for management of groundwater <br /> impacts is technically soared. <br /> REMEDIAL STRATEGY FOR THE 601 EAST MINER STREET SITE <br /> The overall remedial strategy for the 601 East Miner Sheet site Wilizes a combination of <br /> aggressive source control coupled with amounted natural attenuation of the groundwater <br /> impacts. As was discussed in the previous section, the technical basis for selection of <br /> monitored rutuml ahemration for groundwater aspects is based upon site-specific data <br /> generated during the past six years. Modifications to the groundwater monitoring and <br /> sampling pmgrom required to further doeumcot rislurd alternation processes will be <br /> identified in later sections of this letter addendum. <br /> �.mmemusst.Rmr�yw�vrnsoroua.m..ma.i mro��� <br />